Base seat of a ball chair



FIG. 1 is a perspective view of a base seat of a ball chair showing mynew design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof; and,

FIG. 4 is a perspective view showing the design in use, in which thebase seat is installed with a back and wheels of a ball chair.

The broken lines shown in FIGS. 1-4 depict environmental structure andportions of the base seat of a ball chair that form no part of theclaimed design.

CLAIM The ornamental design for a base seat of a ball chair, as shownand described.